Method of, and device for, dampening noises, caused by propellers and other quickly moving bodies



Sept. 10, 1929. F. KRUCKENBERG 1,727,720-

METHOD OF, AND SERVICE FQR, DAMPENING NOISES, CAUSED BY I PRQPELLERS AND OTHER QUICKLY MOVING BODIES Filed March 9, 1928 Patented Sept. 10,1929.

UNITED STATES FRANZ KRUCKENBERG, F HEIDELBERG, GERMANY.

METHOD OF, AND DEVICE FOR, DAMPENING NOISES, CAUSED BY PROPELLERS AND OTHER QUICKLY Application filed March 9, 1928, Serial No.

This invention relates firstly to a method of damping the noises caused by quickly moving and rotating machine-parts or other obiects, for instance quickly rotating propellers,

high-speed tram-cars, high-speed railwaycars and the like, and secondly to a device for practicing that method. Another object of the invention is to keep the respective noises off buildings and the like located in the neighbourhood of the bodies producing the noises. The ends in view 'are attained by the provision of sound-damping or reflecting walls arranged in a suitable manner relatively to the I res ective buildings or other places.

uitable arrangements and combinations of the parts concerned are illustrated diagrammatically and by way of example on the accompanying drawing, on which Figure 1 is a side-view of the rear portion of a highspeed vehicle, driven by a propeller located at that end; Figure 2 is a similar view showing,

however, the front end of such a vehicle with the propeller located at this end Figure 3 is a perspective representation of the rear end no of a high-speed railway vehicle also driven by a propeller, located at that end, and Figure 4 shows a modification, in which the propeller of the high-speed railway vehicle is arranged at the front end 'of the same.

On the drawing (Fig. 1) 5 denotes a suspended railway-car, more precisely the rear end of a high speed suspended railway-car, and 7 is an. annular Wall encompassing the propeller 6. This wall consists of a material especially suited for damping purposes, and its thickness in axial direction is preferably that, indicated in Fig. 1 in dotted lines, that is to say, it is reduced in thickness in the direction of'the front edge and to the rear edge of the annulus, and the thicknest part lies nearer to the front edge than to the rear edge, whereby the resistance, which the annulus offers to the air becomes the smallest possible and the streaming away of the air proceeds in the most favourable way. First of all, the sound waves are prevented from propagating radially with respect to the propeller. The dotted line 8 shown only on the top of the annulus 7 indicates the boundary of the air current produced by the propeller, if no annu- MOVING BODIES.

260,397, and in Germany March 12, 1927.

lus like 7 or equivalent member is provided, and the lines 9, which of course, must be assumed to extend forth from the propeller on its entire circumference indicate the sound waves, which the propeller produces. The intensity of these waves increases from the hub of the propeller to the ends of its blades. The lines 10 and 11 include that space, which the sound waves cannot enter because of the provision of the damping annulus 7. The direction of these latter two lines, or the shape of the space they enclose, will vary with the speed of the vehicle. If that speed becomes greater and greater the line 10 will finally extend vertically and the line 11 horizontally.

The wall of the damping ring 7 is preferably designed as an elastic-solid skin in order to render it as indifferent as possible in acoustic respect. Aparticularly suitable material, which not only is very elastic, but also is of low Weight, and non-resonant, is scum-rubber, which is a rubber mass enclosing very many gas-bubbles.

In Fig. 2 the shape of the damping ring 7 is somewhat different from that shown in Fig. 1, in that its radius becomes gradually shorter in forward direction. I wish it to be understood, however, that this is merely an example. As to the thickness of the wall of the ring, the proportions are practically the same as in ig. 1.

In Figs. 3 and 4 the assumption is made, that a suspended high-speed railway-car is just stopping at a station. 12 indicates the platform of the latter. The annular damping member 7 is carried at its top by a longitudinal member 13, extending along the top of the vehicle (for particulars as regards to this member see the U. S. Patent 1,628,595) and at its sides by fin-like parts 14. As

viewed in plan, thering 7 and the outer end damping ring in such cases protects persons from being hurt by the blades of the pro- 'peller.

Be .it understood, that the damping wall, which can be shaped annular or in any other suitable way, need not be connected with the vehicle or other object, producing the soundwaves. It may be arranged completely separate therefrom. For instance there may be erected stationary walls at certain places along a railway-line, the shape or the arrangement, or both, being so chosen, that the sound-waves are deflected to a direction in Which they are not further disturbing the neighbourhood.

I claim:

1. The method of damping noises caused by propellers and other quickly moving parts, for instance quickly rotating parts, high-speed tram-cars, high-speed railwaycars and the like included, consisting in intercepting the respective sound-waves by sound-damping or sound-reflecting surfaces provided in suitable position at the places to be protected from being disturbed by those waves, substantially as set forth.

2. The method of damping noises caused by propellers and other quickly moving parts,

for instance quickly (rotating parts, highspeed tram-cars, high-speed railway-cars and the like included, consisting in intercepting the respective sound-waves by sound-damping or sound-reflecting walls arranged in suitable position at the places to be protected from being disturbed by those waves, substantially as set forth.

3. A device for damping noises caused by .the propellers of propeller-driven high-speed railways, comprising in combination with the respective propeller, an annular member encompassing it, the sectional area of said member in the axial direction of the same being designed'according to stream-lines, substantially as set forth.

l 4. A device for damping noises caused by the propellers of propeller-driven high-speed railways, comprising in combination with the respective propeller, an annular member encompassing it, a top rib and lateral finlike parts, connecting said member with the body of the respective car, substantially as set forth.

In testimony whereof I affix my signature.

FRANZ KRUCKENBERG. 

